1. Field of the Invention
This invention relates to a desensitizing composition and a desensitizing method. More particularly, it relates to a desensitizing composition which decreases or eliminates the function of an adsorbent capable of causing the color-formation of a colorless color former and to a method of desensitizing an adsorbent comprising using such composition.
2. Description of the Prior Art
It has long been known to form a color image through the reaction of a color former (a nearly colorless organic compound) and an adsorbent. This color-forming reaction has been, for example, applied to recording materials as described in U.S. Pat. Nos. 2,505,470, 2,505,489, 2,548,366 and 2,550,471; recording materials as described in U.S. Pat. Nos. 2,712,507, 2,730,456, 2,730,457 and 3,293,060; recording materials as described in U.S. application Ser. No. 40,732 and British Pat. No. 825,354; and other recording materials for spirit printing, stencil printing, automatic, ticket vending systems, finger printing systems letter writing systems, and the like.
In these recording materials, the color former and the adsorbent cause a color reaction when they come into contact, and, therefore, it is desired to prevent, by some means, color reaction in areas in which the formation of a color image is not required, from the viewpoint of performance and cost. For this purpose, desensitizers have so far been used, and there are known, for example, high molecular weight primary alkylamines such as dodecylamine, quaternary ammonium salts such as dodecyltrimethylammonium chloride and alkyl or arylamine acetates, as described in Japanese Patent Publication No. 3,921/58; monoalkylamines, aralkylamines and tertiary amines comprising ethanolamine chemically bonded with an ethylene oxide group, as described in Japanese Patent Publication No. 29,546/71; precondensates of urea resins as described in Japanese Patent Publication No. 35,697/71; secondary alkylamines such as didodecylamine, tertiary alkylamines such as triethylamine, primary arylamines such as aniline, aralkylamines such as benzylamine, polyhydroxy compounds such as polyethylene glycol or glycerol, etc.
However, these desensitizers are disadvantageous in that their desensitizing effect is insufficient, or even if they show a satisfactory effect, practically useful effects cannot be obtained unless they are used in large amounts. Therefore, the use of some desensitizers results in color formation in the desensitized areas even when used in large amounts; in particular, this defect tends to become more serious as color formers and adsorbents are improved.
For example, color formers having a fluoran nucleus are particularly difficult to desensitize as compared with Crystal Violet lactone, and the like. Moreover, the above desensitizers scarcely show a desensitizing effect on adsorbents such as phenol resins and metal salts of aromatic carboxylic acids. Therefore, the effective use of the advantageous properties of these adsorbents (for example, color images obtained using them do not disappear under the action of water) is restricted. Another defect of the conventional desensitizers is that when a solution of a color former which is microencapsulated is brought into contact with a desensitized adsorbent, the undesensitized areas of the adsorbent cause color formation with the passage of time (fogging).
In addition, conventional desensitizers often yellow on the adsorbents, or they have slow drying rate since they are used in a large amount, and therefore, it is difficult to increase the coating (printing) rate.